Polini 130 Grauguss - was kann er wirklich?

[keuk]

Hello,

I just come back from the Run & Race, it was awesome, nice race with cool german people !

I need some advises for my setup

Polini 130 + GS piston

Malossi cylinder head gravedigerised

Racing Cranckshaft mazzuchelli (not lip)

4th DRT

Ratio 2,86

Clucth renforced 4 discs with softer spring than the malossi

Koso 28

Polini reedvalve with stage6 membran

28mm intake

Vespatronic

Diagram 186 / 121 / squich 1mm (i only touch the exhaust port and i made the cylindre 2 and 3mm machined)

First try at Mirecourt on Maxiscoot Dyno 16PS

Koso setup 135/42/ Needle Keihin JJJ 2nd position from top

Exhaust PM40

Second try at Run&Race 09 less than 16 but better revolutions

Koso setup 128/42 Needle Keihin JJJ 3rd positon from top

Exhaust Franz

I tought i can have more power with the franz but i think i'll have to modify my setup, do you have any advise ? too rich ? clucth too soft ? need to update the diagramms ?

More pictures of the motor here:

Polini 130 build

Thanx for your help .

Bearbeitet 17. Juni 2009 von keuk

[heizer]

I think you need more exhaust time, go more to 126-130 and exhaust 186-190.

And lip your crankshaft.

[Brosi]

Looks like exhaust blowdown area might be to small.

Do you have a portmap or picture of the exhaust port? How wide is it? What form?

No bottlenecks between piston and exhaust pipe side?

[keuk]

Looks like exhaust blowdown area might be to small.

Do you have a portmap or picture of the exhaust port? How wide is it? What form?

No bottlenecks between piston and exhaust pipe side?

I will make a portmap and take pictures tonight, i didn't update the exhaust port since i put the GS piston...

[sirnick1986]

I will make a portmap and take pictures tonight, i didn't update the exhaust port since i put the GS piston...

You need rotary valve.... if you really want to catch horse power

[Brosi]

You need rotary valve.... if you really want to catch horse power

If it is´n an insider, it´s just bullsh*t.

[FalkR]

@keuk

How much exhaustport width do you have?

Which diameter has the exhaust flange?

Optimize your crankshaft!

How did you adjuste the vespatronic ignition? 24° to 16° TDC?

Like Brosi and heizer also said before, the cylinder need more inlet-time. A higher exhaust-time isn't absolutley necessary to reach the 18hp region with these requirements (Polini, GS, Franz, 28mm carburator, vespatronic etc.)

Good Luck

Edit: Are you sure that your exhaust-time is 186°? Your peak is very early for this time. Normally engines with these port timings peak in region aboout 8000 to 8500 rpm. To check the timings again does no harm.

There i got something mixed up in my mind this morning, your peak ist totally normal...

Bearbeitet 17. Juni 2009 von FalkR

[keuk]

@keuk

How much exhaustport width do you have?

Which diameter has the exhaust flange?

Optimize your crankshaft!

How did you adjuste the vespatronic ignition? 24° to 16° TDC?

Like Brosi and heizer also said before, the cylinder need more inlet-time. A higher exhaust-time isn't absolutley necessary to reach the 18hp region with these requirements (Polini, GS, Franz, 28mm carburator, vespatronic etc.)

Good Luck

Edit: Are you sure that your exhaust-time is 186°? Your peak is very early for this time. Normally engines with these port timings peak in region aboout 8000 to 8500 rpm. To check the timings again does no harm.

There i got something mixed up in my mind this morning, your peak ist totally normal...

Thanks FalkR, for the vespatronic i have adjusted it like on the picture bellow.

I'll take all the measure for the exhaust tonight, the inlet port is the polini original, and for the exhaustport width i'm far from the 72% ? allowed by the gs piston. the exhaust flange is 32mm diameter (i have adjusted it for the pm40).

Bearbeitet 17. Juni 2009 von keuk

[FalkR]

Okay, but did you check the ignition with strobe light? Sometimes there are some deviations because of manufacture tolerances.

My ignition started in this setting on the picture at 27° TDC at 2000rpm for example (checked with strobe light). -> too much pre-ignition causes thermic problems

I won't trust on standard basic settings, so i check it everytime i build in a new part that could change the settings.

GS piston maximum in regard to the width is ca. 72% of the bore.

As suitable for everyday life it had exposed that 70% is a good average which doesn't charge the rings to heavy and ensure not such a high wareout.

Are you going to raise the cylinder so that inlet-time of the transfer ports goes to 126° or something like that?

Bearbeitet 17. Juni 2009 von FalkR

[salih]

Thanks FalkR, for the vespatronic i have adjusted it like on the picture bellow.

You should check the correct timing with a timing light asap... I also adjust my vespatronic for the first time like on the pic, the ignition timing was round about 35°

[FalkR]

35° ist krass

[salih]

35° ist krass

Meine Skala am Motor geht zum Glück bis 40° Gut dass ich das Bild nur als Anhaltswert zum Abblitzen genommen hab, sonst hätte mir der Motor was erzählt *klingeling*

[keuk]

Okay, but did you check the ignition with strobe light? Sometimes there are some deviations because of manufacture tolerances.

My ignition started in this setting on the picture at 27° TDC at 2000rpm for example (checked with strobe light). -> too much pre-ignition causes thermic problems

I won't trust on standard basic settings, so i check it everytime i build in a new part that could change the settings.

GS piston maximum in regard to the width is ca. 72% of the bore.

As suitable for everyday life it had exposed that 70% is a good average which doesn't charge the rings to heavy and ensure not such a high wareout.

Are you going to raise the cylinder so that inlet-time of the transfer ports goes to 126° or something like that?

You should check the correct timing with a timing light asap... I also adjust my vespatronic for the first time like on the pic, the ignition timing was round about 35°

- I will check the ignition with my strobe light asap.

- For the 70% schould i take the width measure on the portmap or the measure directly on cylinder ? I think "Sehnenmaß" is more logical

- To raise the 126° i really don't know, i know that it's dangerous to touch the shape of the inlet ports, but i would like not to use a spacer..... any aproximative idea of how much millimeters i should increase ?

Bearbeitet 17. Juni 2009 von keuk

[Johannes]

You should check the correct timing with a timing light asap... I also adjust my vespatronic for the first time like on the pic, the ignition timing was round about 35°

hm... aus Faulheit habe ich (und andere) da nie geblitzt. Habe diese Flucht immer für ne Standard Weichei Einstellung gehalten und einfach mal pauschal noch um 2-3mm weiter in Richtung früh verstellt. Wenn meine Toleranzen ähnlich fallen hätt ich da an die 40° gehabt. Motor lief aber unauffällig. Naja, ich glaub ich sollte bei meinem neuen Motor doch mal die Blitzpistole auspacken...

[FalkR]

70% in "Sehnenmaß" is 39,9mm -> calculated in mm of the bore : 44,2mm

To reach 126° you have to raise the cylinder ca. 0,9mm with a spacer. BUT you have to lathe face of the top from the cylinder about 0,9mm to have the same travel and the same squish.

According to time calculator progs like RACE BASE CALCULATOR , the exhaust rising has a negative amount!

So if you would take a spacer with 0,9mm you have a exhaust-time about 190° and a inlet-time about 126° and a pre-exhaust-time about 32°.

I didn't test that timings, yet. But i think the creator of the exhaust "Franz" -> "amazombi" could give you some information whether it works great or not.

Bearbeitet 17. Juni 2009 von FalkR

[Johannes]

if it's a dedicated racing engine I would raise the cylinder by 1.5mm (and mill the head down by 1.5mm, too). Thus you should have 129,7° / 192,6° - this will definitely work very well with a "Franz" exhaust...

...and of course the exhaust port has to be shaped and widened to 70% bore width, as said by FalkR

Bearbeitet 17. Juni 2009 von Johannes

[keuk]

if it's a dedicated racing engine I would raise the cylinder by 1.5mm (and mill the head down by 1.5mm, too). Thus you should have 129,7° / 192,6° - this will definitely work very well with a "Franz" exhaust...

...and of course the exhaust port has to be shaped and widened to 70% bore width, as said by FalkR

Yes that's a race engine but if i raise the cylinder i will have to work the bottom of each port, exhaustport , inlet port, 3rd port, isn't that easier to work only on the top of the inlet port without raising the cylinder ?

I will ask Mathias for the ideal timing of his exhaust.

[Johannes]

Yif i raise the cylinder i will have to work the bottom of each port, exhaustport , inlet port, 3rd port

why? that's not necessary, it's really just the 1.5mm spacer...

[FalkR]

Yes that's a race engine but if i raise the cylinder i will have to work the bottom of each port, exhaustport , inlet port, 3rd port, isn't that easier to work only on the top of the inlet port without raising the cylinder ?

I will ask Mathias for the ideal timing of his exhaust.

If you raise the cylinder you haven't to work at each port (exhaust, inlet usw). To work only on the top of the inlet ports it's very difficult to reach the same angle of the inlet ports towards the tenure of the piston.

To get the cylinder to 192/129, like Johannes said, you only have to raise the cylinder about 1,5mm and mill the top about 1,5mm

Edit: too slow

Bearbeitet 17. Juni 2009 von FalkR

[keuk]

why? that's not necessary, it's really just the 1.5mm spacer...

Because i thought it was a problem when the bottom of the port were higher or lower than the bottom of the piston. So i though it was necessary to increase the bottom of "X" on my drawing.

[FalkR]

Bringt es eigentlich was, die Nebenüberströmer und die BoostPort-Kanäle auf das selbe Niveau der Hauptüberströmer zu bringen?

Lohnt sich sowas? Wer hat es schonmal ausprobiert? Was ist bei rumgekommen?

Und vorallem wer kann sowas?

Bearbeitet 17. Juni 2009 von FalkR

[Johannes]

Because i thought it was a problem when the bottom of the port were higher or lower than the bottom of the piston. So i though it was necessary to increase the bottom of "X" on my drawing.

The difference between "piston aligned to transfer bottom" and "piston 1.5mm below transfer bottom" is extremely small. And that only if you're doing the job right (that means port increased at the full length with the right angles!!). If you just lower the transfer ports at the liner surface, they'll probably flow worse than untouched...

Bearbeitet 17. Juni 2009 von Johannes

[keuk]

That's clear, i will try to use the port mapping calculator, what is the size of the conroad and its stroke on mazzuchelli ?

Bearbeitet 17. Juni 2009 von keuk

[FalkR]

stroke mazzu : 51mm

conrod : 97mm

Bearbeitet 17. Juni 2009 von FalkR

[KTy]

Stop telling him how to make a powerfull engine damn'it ! He is already wayy faster than me on the track :-D

[heizer]

Stop telling him how to make a powerfull engine damn'it ! He is already wayy faster than me on the track :-D

[Luccio]

yes 15hp is enough for him.....please tell him bullshit

[salih]

If you race in class 1, then it's unnecessary to check the ignition, really...

[keuk]

If you race in class 1, then it's unnecessary to check the ignition, really...

Hey !!

[amazombi]

I will ask Mathias for the ideal timing of his exhaust.

Mathias says that everything Johannes wrote is perfectly accurate. The only addition I may want to make would be that with exhaust timing of around 190° and over you will find more power and more overrev. You may loose some power lower down the rev range, what you get on top usually more than compensates for that. At the end of the day it's a question of personal preference though, and I, as a mediocre rider, have found it easer to ride fast with a slightly lower strung engine.

Bearbeitet 17. Juni 2009 von amazombi